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Finding the Fourth Proportional to 991.80, 1,369.78 and 661.74

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Solution

The fourth proportional to 991.80, 1,369.78 and 661.74 is: 913.93

Step by Step Solution

  1. Step 1: Write the proportion equation
    991.80 : 1,369.78 = 661.74 : x
  2. Step 2: Convert to fraction form
    991.80/1,369.78 = 661.74/x
  3. Step 3: Cross multiply
    991.80x = 1,369.78 × 661.74
  4. Step 4: Simplify right side
    991.80x = 906,438.22
  5. Step 5: Solve for x
    x = 906,438.22/991.80
  6. Step 6: Final answer
    x = 913.93

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.